Abstract:Objective:To substantiate the effect of weightlessness and heavy ion radiation in sapce environment on medicinal plants.Methods:The seeds of medicinal plant Carthamus tinctorius were carried aboard a retrievable stellite during 3～18 July,1994.After returning to earth,the changes of peroxidase and protein were studied by means of electrophoresis.Results:The result showed that the peroxidase activity of each group of seeds which were hit and penetrated by heavy ion rays was higher than that of the ground controlled seeds,but slightly lower than that of the weightless seeds.The protein contents of the weightless seeds and the seeds which were penetrated once and less than once by heavy ion rays were higher than those of the seeds which were kept on earth,but the seeds which were penetrated 2～3 times by heavy ion rays were lower than those of the ground controlled seeds.The peroxidase isozyme and protein patterns of the weightless seeds were similar to those of the ground controlled seeds,but very different between the heavy ion ray penetrated seeds and the earth kept seeds.Conclusion: It follows that the weightlessness in space environment has an effect mainly on the physiological condition of plants,but the heavy ion radiation has a stronger effect on the hereditary basis of plants.